Britannica
Sources used in this answer
When does the embryonic period begin and end in human development?
Created from Britannica articles
using AI.
AI can make mistakes, so verify using Britannica articles.
prenatal development
An ultrasound image of a human fetus.
In human prenatal development, the embryonic periodāalso known as the period of organogenesisābegins at the start of the third week of development and concludes at the end of the eighth week.1
While some sources note that the term embryo is applied until the end of the seventh week, with the transition to the fetal period occurring at the start of the eighth week, the embryonic stage is generally defined as spanning from the third through the eighth week of development. During this critical phase, the tissues and organs of the body are formed, and by the end of the stage, the developing organism is clearly distinguishable as a human.21